Why does Parallel.ForEach change the culture of its threads?

Question

Today I came across a strange phenomenon I can't really explain. There's a webpage with a number of rows in a gridview, which need to be saved to the database and to an XML file one by one. I ended up using a Parallel.ForEach, as there is no relation between the rows, so they can be executed independently. The code is basically this:

        Parallel.ForEach(gvWithData.Rows.Cast<GridViewRow>(), row =>
        {
            if (row.RowType == DataControlRowType.DataRow)
            {
                    // do some logic and stuff...
                    var type = new Object { ... };

                    // save to the database
                    type.Save();

                    // retrieve the saved item from the database again
                    //  since we need some autoincrement values from the db
                    var typeAfterSave = TypeManager.GetFromDb();

                    // create a custom XML from the object
                    XmlManager.CreateXml(typeAfterSave);
                }
            }

Why on earth would this code work any different when I replace the Parallel.ForEach with a good old foreach and I change nothing else?

The difference is that the culture in which the XML is created in the first case is different from the second case, and I have not the slightest clue why.

Any suggestions?

Merchant

Culture can be stored as a thread local. If you changed the culture of the active thread it does not affect thread pool threads. – Roy

Answer 1

It's because you've set culture for the CurrentThread. Parallel.ForEach will create a new Task for every iteration, which they will have the default culture.

In .NET 4.5, you can use the CultureInfo.DefaultThreadCurrentCulture property to change the culture of an AppDomain ( set the culture for all threads ).

(CultureInfo.DefaultThreadCurrentCulture on msdn)

Tine

Thanks for the answer! You are correct. Unfortunately this application is still using 4.0 with no option to change this before the next release. I resolved to setting the culture settings just inside the loop. Appreciated! – Merchant

Your're welcome, As you said you can set culture thread inside the loop. – Tine